7.9.1 release

[jmlrt]

This PR prepare 7.9 branch for 7.9.1 release:

• bump chart and Docker images version from 7.9.1-SNAPSHOT to 7.9.1
• remove notices on README that this is a development branch and development branch specific install instructions

Note

• remove notices on README that this is a development branch and development branch specific install instructions

This is required because released Helm charts will be packaged from this PR commit including the README files that will be available inside the chart packages and in Helm Hub pages (example: Elasticsearch chart page).

This change will be reverted in the next PR after release when we will bump 7.9 branch to 7.9.2-SNAPSHOT version.

[jmlrt]

7.9.1 - 2020/09/03

• 7.9.1 as the default stack version
• Helm 2.16.10 support in #797 @jmlrt
• Drop GKE 1.14 tests in #798 @jmlrt

APM Server

PR	Author	Title
#763	@ebuildy	Remove duplicate initialDelaySeconds field
#786	@caiconkhicon	Fix serviceAccount

Elasticsearch

PR	Author	Title
#752	@AhmedSamirAhmed	Remove elastic-certificate-crt in security example clean target

Logstash

PR	Author	Title
#776	itssimon	Fix headless service ports spec

Metricbeat

PR	Author	Title
#770	vliubko	Add missing labels for deployment

[ghost]

jenkins test this please